Accuracy and precision. Serum samples from 2 normal donors (represented by gray and black), diluted 10-fold with PBS, contained the indicated known final concentrations of purified sCD22-Fc. ELISA-determined sCD22 concentrations in the samples were compared with known concentrations to determine accuracy (A) and precision (B). COV indicates coefficient of variance. Shown are the means of 2 or 3 independent experiments, and error bars represent SD.